1. Field of the Invention
The present invention relates to a liquid discharge head for discharging liquid and the driving method therefor, and a cartridge formed integrally with a liquid tank retaining liquid to be supplied to the liquid discharge head. The invention also relates to an image forming apparatus to form images on a printing medium. The invention is not only applicable to the printing apparatuses generally in use, but also, to a copying machine, a facsimile equipment provided with communication systems, and an apparatus having a printing unit, such a word processor, as well. Further, the invention is applicable to an industrial recording system having various processing apparatuses complexly combined therein, and also, to a textile printing apparatus and a processing apparatus such as to perform etching or the like.
Here, the term xe2x80x9cprintingxe2x80x9d or xe2x80x9crecordingxe2x80x9d used for the specification hereof means not only the formation of meaningful information, such as characters, graphics, but also, it is meant to include, in a broad sense, images, designs, patterns, or the like formed on a printing medium, as well as to include processes such as etching, irrespective of being meaningful or meaningless, or being apparent to be visually recognizable by eyesight. Also, the term xe2x80x9cprinting mediumxe2x80x9d means not only the paper sheet that is usually used for a printing apparatus in general, but also, it means cloth, plastic film, metallic plate, glass, ceramic, wood, leather, or the like, which is capable of receiving ink. The printing medium may be a sheet, a three-dimensional object, such as a spherical or cylindrical one, among some others. Further, the term xe2x80x9cliquidxe2x80x9d should also be interpreted in a broad sense as in the definition of the xe2x80x9cprinting (or recording)xe2x80x9d as described above, and it is meant to include the one used for a printing medium to form images, designs, patterns, or the like, or used for etching process of a printing medium or ink processing (such as coagulating or insolubilizing coloring materials in ink to be used for a printing medium).
2. Related Background Art
An ink jet printer is the printing apparatus of the so-called non-impact printing type, which is capable of performing printing at higher speeds on various kinds of printing mediums. Therefore, with its feature that almost no noises are generated when printing, the ink jet printer is widely adopted as an apparatus that operates a printing mechanism for a word processor, a facsimile equipment, or a copying machine.
As the typical ink jet method, there is known the one that uses the electrothermal transducing elements that generate thermal energy as energy for discharging liquid, namely, ink droplets, such as processing liquid (hereinafter, these are collectively called xe2x80x9cinkxe2x80x9d for convenience sake in the specification hereof) which is used for adjusting the printability of ink with respect to ink itself or a printing medium. The ink jet method makes it possible to discharge small ink droplets from extremely fine discharge ports for printing on paper or some other printing medium.
Generally, the ink jet head uses electrothermal transducing elements comprising a driving system to form ink droplets, and a supply system to supply ink to the driving system. This head has the electrothermal transducing elements in a pressurized chamber. Then, the electric pulses which become printing signals are applied to them so that thermal energy is given to ink, and the abrupt changes occurring in the phases of ink at that time, that is, the bubbling pressures generated by vaporization, are utilized for discharging ink droplets.
Also, for the ink jet head using electrothermal transducing elements, there are known an edge shooter type where ink is discharged from the surface of the base plate in the arrangement direction of the electrothermal transducing elements, and a side shooter type where ink is discharged vertically from the surface of the base plate having the electrothermal transducing elements arranged thereon.
FIG. 48 is a view which shows the external appearance of an ink jet head of side shooter type in accordance with the background art hereof. FIG. 49 is a view which schematically shows the structure thereof. FIG. 50 and FIG. 51 are cross-sectional views which illustrate the structure thereof, taken in line 50xe2x80x9450 and line 51xe2x80x9451 in FIG. 49, respectively. In other words, for each of the heat generating base plates 12 where electrothermal transducing elements 11 are arranged at specific intervals, there are formed a plurality of discharge ports 13 for discharging ink, plural ink chambers 14 having these discharge ports 13 open therefrom, and a long and narrow ink supply port 15 for supplying ink to each of these ink chambers 14. The ink supply port 15 which extends in the arrangement direction of electrothermal transducing elements 11 is generally cut and provided for the heat generating base plate 12 by means of sand blasting, anisotropic etching, or laser processing. Also, the electrothermal transducing elements 11 are connected with a wiring base plate 16 and each heat generating base plate 12 through the TAB (tape automated bonding) method for the application of electric signals for discharging ink. Further, each heat generating base plate 12 is fixed to a supporting member 17, respectively.
In recent years, along with the significant reduction of costs and higher performance of a personal computer, the use of color printers has been promoted more. The printing head of a color printer of the kind should use ink of many colors, and it is arranged in plural numbers. For example, four heads are provided to use four colors, such as yellow, magenta, cyan, and black, and also, in order to make the apparatus smaller, each of the electrothermal transducing elements 11 is arranged on the heat generating base plate 12 at as smaller intervals as possible. For a highly precise printer having an ink jet head capable of performing at 600 dpi or 1,200 dpi, for example, it is required to form each of the discharge ports 13 and ink chambers 14 with an extremely high uniformity. As a result, it is generally practiced that each ink chamber positioned on either edge in the arrangement direction of the discharge ports 13 is regularly made a dummy ink chamber 14d, and that each of such dummy chambers is discriminated from the ink chambers 14 which are used for the actual printing operation.
Conventionally, as an ink jet head, there has been known the one which drives the driving elements, such as piezoelectric elements or electrothermal transducing elements, to discharge, liquid by the application of pressure or by means of bubble generation. Since an ink jet head of the kind deals with liquid, the arrangement is made to exhaust the liquid which has become overly viscous outside the head from the interior thereof. For this purpose, a suction recovery mechanism that uses a cap is arranged, and the pre-discharge (that is, idle discharges without any relations to printing signals) is performed to drive the driving elements, or a cleaning mechanism is provided for the ink jet printer to clean the surface of the discharge ports.
For an ink jet printer of the kind, a mode is adopted so that the xe2x80x9csuction recoveryxe2x80x9d, xe2x80x9ccleaningxe2x80x9d, or xe2x80x9cpre-dischargexe2x80x9d is performed as the operational sequence therefor or a mode is adopted so that the xe2x80x9cpre-dischargexe2x80x9d is performed only after the xe2x80x9ccleaningxe2x80x9d is executed.
Meanwhile it has been known to make a color printer available by installing a plurality of ink jet heads thereon. However, irrespective of the case where a plurality of color ink jet heads are integrally formed or where these heads are individually arranged, liquids of different colors or different properties may be mixed between a plurality of ink jet heads in some cases.
Various means have been introduced in order to overcome these drawbacks. Particularly, as-among such means, a technique has been disclosed in the specification of Japanese Patent Application Laid-Open No. 08-295033 whereby to provide dummy nozzles each between the adjacent ink jet heads for the prevention of color mixture between them. More specifically, ink is induced to the dummy nozzle from the adjacent ink jet head, and then, ink of mixed colors is discharged from the dummy nozzle to make it possible to remove such ink of mixed colors.
For the ink jet head shown in FIGS. 48 to 51, which is related to the background art, the area of each dummy ink chamber 14d requires a certain dimension to provide this area. Here, it is not good enough just to provide a dummy ink chamber 14d alone. For the ink jet head shown in FIGS. 48 to 51, which is related to the background art, each of the discharge ports 13, which is arranged corresponding to a dummy ink chamber 14a and a dummy ink chamber 14a, respectively, is formed in the same shape and dimension at the same arrangement pitches as each of the ink chambers 14 and discharge ports 13 to be used for printing. As a result, for an ink jet head having highly precise pitches at which the discharge ports 13 are arranged, the numbers of dummy ink chambers 14d and the discharge ports 13 are inevitably increased. Then, it becomes impossible, in some cases, to remove bubbles completely from the dummy ink chambers 14d when ink is sucked altogether from each of the discharge ports 13 of plural ink jet heads using ink of plural colors when the recovery process is executed to keep the ink discharge from each of the discharge ports 13 in good condition for such ink jet heads. This may lead to a condition where ink of different color is induced into each of the dummy ink chambers 14d the inner pressure of which has been reduced, with a possibility that ink of plural colors are mixed in the ink jet head. Also, a drawback is encountered that ink is sucked and exhausted from the dummy ink chambers 14d when the recovery process is executed, thus inevitably increasing the amount of ink wastefully consumed.
In the meantime, when the surface of the discharge ports is wiped off using the wiper blade, ink which adheres to the wiper blade or to the surface of the discharge port may be pressed into the discharge ports in some cases. Such ink that may be pressed into the discharge port is usually mixed with different colors or in a state of being overly viscous, which necessitates a pre-discharging operation after the wiping operation so as to exhaust such ink outside for the intended execution of a high quality printing.
In this respect, the discharge ports which have been wiped off earlier have a longer period of time during which mixed ink is dispersed in them than the discharge ports which are wiped off later. Therefore, if the pre-discharges are operated in the same order as that of the wiping operation given to the discharge ports, it becomes possible to remove ink of mixed colors with the lesser frequency of pre-discharges.
As described above, one of the objectives to operate the pre-discharges after the execution of suction recovery or wiping is to exhaust outside the ink of mixed colors which is pressed into the ink jet head or to exhaust outside the ink which has become overly viscous. The recovering capability of ink jet head with respect to the pre-discharging operation, that is, the exhausting capability of ink effectuated by such pre-discharges, may differ greatly in some cases at the discharge ports through which the actual printing operation is executed (hereinafter referred to the xe2x80x9cmain discharge portsxe2x80x9d) and at the dummy discharge ports (hereinafter referred to as the xe2x80x9csub-discharge portsxe2x80x9d). In other words, with the amount of liquid discharged from the sub-discharge ports being greater than that of liquid discharged form the main discharge ports in general, the recovering capability of an ink jet recording head is better at the sub-discharge ports per pre-discharging operation. However, since the sub-discharge ports are arranged closer to the portion where the flow of liquid tends to be stagnant, such as the edge portions or the like of the long and narrow common liquid chamber which extends in the arrangement direction of the main discharge ports, it is usually required to set the amount of liquid, which is discharged from one sub-discharge port, much larger than that to be discharged from one main discharge port. Conventionally, however, the recovering capability of the main discharge port and that of the sub-discharge port are not discriminated distinctly. Then, the amount of liquid, which is needed for executing the pre-discharge of each sub-discharge port for securing the recovering capability of the pre-discharge port, is applied equally to the main discharge port. As a result, a drawback is encountered that the amount of liquid which is pre-discharged from the main discharge port should become more than actually needed.
It is an object of the present invention to provide a liquid discharge head which does not present any drawbacks, such as mixed colors, with the liquid being pressed partly into the interior thereof when liquid is sucked altogether from the discharge ports for the execution of recovery process to maintain good condition of plural kinds of liquids and the respective discharges thereof from plural kinds of discharge ports.
It is another object of the invention to provide a liquid discharge head capable of suppressing the wasteful consumption of liquid as much as possible when the recovery process is executed, at the same time, being capable of exhausting bubbles existing inclusively therein.
It is still another object of the invention to provide a method for making liquid flowable despite its tendency to be stagnated on the edge portions of the long and narrow common liquid chamber in the longitudinal direction thereof where liquid is supplied, and then, making it possible to exhaust the stagnated liquid outside reliably, and also, to provide a cartridge formed integrally with the aforesaid liquid discharge head, and a liquid tank retaining liquid to be supplied to the liquid discharge head.
It is a further object of the invention to provide an image forming apparatus for forming images on a printing medium by use of the aforesaid liquid discharge head.
It is still a further object of the invention to provide a liquid discharge head which comprises a plurality of main discharge ports arranged at predetermined intervals; at least one sub-discharge port arranged in the arrangement direction of the main discharge ports on both end sides of the arrangement direction of main discharge ports at intervals larger than the intervals of the main discharge port arrangement; a plurality of liquid chambers having these plural discharge ports open thereto; a common liquid chamber having these liquid chambers communicated therewith, and liquid being supplied thereto; and a plurality of discharge energy generating units provided for each of the liquid chambers corresponding to the main discharge ports and the sub-discharge ports to generate discharge energy utilized for discharging liquid from the main discharge ports and the sub-discharge ports. With the liquid discharge head thus arranged, liquid is discharged from the main discharge ports at the time of printing operation, while the discharge energy generating units in the liquid chambers to which the sub-discharge ports are open do not generate discharge energy so as to discharge no liquid from the sub-discharge ports. However, when pre-discharging operation is performed prior to printing operation, sub-discharge ports can discharge liquid, too. Also, with the sub-discharge ports being arranged at intervals larger than the arrangement interval of, the main discharge ports, the resultant numbers of sub-discharge ports become relatively smaller than the conventional arrangement where all the discharge ports are arranged at predetermined intervals when liquid is sucked from the main discharge ports and sub-discharge ports as well, provided that the arrangement length of discharge ports is specific. Therefore, the suction amount of liquid from the sub-discharge ports can be made relatively smaller.
It is still another object of the invention to provide a method for driving a liquid discharge head, which is provided with a plurality of main discharge ports arranged at predetermined intervals, and at least one sub-discharge port arranged in the arrangement direction of the main discharge ports on both end sides of the arrangement direction of main discharge ports at intervals larger than the intervals of the main discharge port arrangement for discharging liquid from the main discharge ports to a printing medium for printing, comprises the step of discharging liquid from the sub-discharge ports simultaneously in order to make the discharge condition of liquid from the main discharge ports excellent when liquid is discharged from the main discharge ports. With the method for driving the liquid discharge head thus arranged, it becomes possible to discharge liquid from the sub-discharge ports when pre-discharging operation is performed prior to printing operation, and liquid in the liquid chambers to which the sub-discharge ports are open is discharged together with bubbles residing in them.
It is still another object of the invention to provide a method for driving a liquid discharge head, which is provided with a long and narrow liquid common chamber having liquid to be supplied thereto; a plurality of main discharge ports arranged on both sides of the common liquid chamber at predetermined intervals, respectively, in the longitudinal direction of the common liquid chamber; a plurality of sub-discharge ports arranged on both sides of the common liquid chamber in the arrangement direction of the main discharge ports at least on one end side of the arrangement direction of main discharge ports at intervals larger than the intervals of the main discharge port arrangement; and a plurality of liquid chambers having these main discharge ports and sub-discharge ports open thereto, at the same time, being communicated with the common liquid chamber for discharging liquid from the main discharge ports to a printing medium for printing, comprises the step of discharging liquid simultaneously from at least two of the main discharge ports adjacent to each other with having one of the sub-discharge ports and the common liquid chamber between them, the step being executed one after another from one end side in the arrangement direction of the main discharge ports. With the method thus arranged, the step, in which liquid is discharged simultaneously from one of the sub-discharge ports and two main discharge ports adjacent to each other having the common liquid chamber between them when pre-discharging operation is executed prior to printing operation, is executed one after another from one end side in the arrangement direction of the main discharge ports, and then, the liquid, which is in a state of stagnation on one end side in the longitudinal direction of the common liquid chamber, is reliably exhausted from sub-discharge ports.
It is still another object of the invention to provide a method for driving a liquid discharge head, which is provided with a long and narrow liquid common chamber having liquid to be supplied thereto; a plurality of main discharge ports arranged on both sides of the common liquid chamber at predetermined intervals, respectively, in the longitudinal direction of the common liquid chamber; a plurality of sub-discharge ports arranged on both sides of the common liquid chamber in the arrangement direction of the main discharge ports on at least one end side of the arrangement direction of main discharge ports at intervals larger than the intervals of the main discharge port arrangement; and a plurality of liquid chambers having these main discharge ports and sub-discharge ports open thereto, at the same time, being communicated with the common liquid chamber for discharging liquid from the main discharge ports to a printing medium for printing, comprises the steps of:
discharging liquid simultaneously from at least two of the main discharge, ports adjacent to each other with having one of the sub-discharge ports and the common liquid chamber between them when liquid is discharged from the main discharge ports in order to make the discharge condition of liquid from the main discharge ports excellent, the step being provided in plural numbers; operating liquid discharge from one of the discharge ports one after another from one end side in the arrangement direction of the main discharge ports; and operating liquid discharges from at least two of the main discharge ports adjacent to each other having the common liquid chamber between them on one end side and the other end side alternately in the arrangement direction of the main discharge ports. With the method thus arranged, when the pre-discharging operation is executed prior to printing operation, the step, in which liquid is discharged from one of the sub-discharge ports and at least two of the main discharge ports adjacent to each other having the common liquid chamber between them simultaneously, is repeated, but whereas the liquid discharge from one of the sub-discharge ports is performed one after another from one end side in the arrangement direction of the main discharge ports, the liquid discharges from at least two of the main discharge ports having the common liquid chamber between them are executed alternately on one end side and the other end side in the arrangement direction of the main discharge ports. As a result, vibration is given to the liquid which is in a state of stagnation on both end sides in the longitudinal direction of the common liquid chamber to promote its flowability, thus exhausting it from the sub-discharge ports reliably.
It is still another object of the invention to provide a method for driving a liquid discharge head, which is provided with a long and narrow liquid common chamber having liquid to be supplied thereto; a plurality of main discharge ports arranged on both sides of the common liquid chamber at predetermined intervals, respectively, in the longitudinal direction of the common liquid chamber; a plurality of sub-discharge ports arranged on both sides of the common liquid chamber in the arrangement direction of the main discharge ports on at least one end side of the arrangement direction of main discharge ports at intervals larger than the intervals of the main discharge port arrangement; and a plurality of liquid chambers having these main discharge ports and sub-discharge ports open thereto, at the same time, being communicated with the common liquid chamber for discharging liquid from the main discharge ports to a printing medium for printing, comprises the steps of discharging liquid simultaneously from at least two of the main discharge ports adjacent to each other with having one of the sub-discharge ports and the common liquid chamber between them when liquid is discharged from the main discharge ports in order to make the discharge condition of liquid from the main discharge ports excellent, the step being provided in plural numbers; dividing the-main discharge ports into a first group and a second group one after another alternately in the arrangement direction thereof from one end side in the arrangement direction thereof; operating liquid discharge from the sub-discharge ports one after another from one end side in the arrangement direction of the main discharge ports; selecting form the first group the first and last sub-discharge ports positioned on one end side in the arrangement direction of the main discharge ports, and at least two of the main discharge ports each discharging liquid simultaneously; and selecting from the second group at least one of the discharge ports other than the first and last sub-discharge ports positioned on one end side in the arrangement direction of the main discharge ports, and at least two of the main discharge ports discharging liquid simultaneously. With the method thus arranged, when the pre-discharging operation is executed prior to printing operation, the step, in which liquid is discharged from one of the sub-discharge ports and at least two of the main discharge ports adjacent to each other having the common liquid chamber between them simultaneously, is repeated, but the liquid discharge from form the sub-discharge port is executed one after another from the one end side in the arrangement direction of the main discharge ports. The main discharge ports are divided into a first group and a second group one after another from one end side in the arrangement direction thereof. The first and last sub-discharge ports positioned on the one end side in the arrangement direction of the main discharge ports, and at least two main discharge ports which discharge liquid simultaneously, respectively, are selected from the first group. However, at least one of sub-discharge ports other than the first and last sub-discharge ports positioned on one end side in the arrangement direction of the main discharge ports, and at least two of the main discharge ports which discharge liquid simultaneously are selected from the second group.
It is still another object to the invention to provide a method for driving a liquid discharge head, which is provided with a long and narrow liquid common chamber having liquid to be supplied thereto; a plurality of main discharge ports arranged on both sides of the common liquid chamber at predetermined intervals, respectively, in the longitudinal direction of the common liquid chamber; a plurality of sub-discharge ports arranged on both sides of the common liquid chamber in the arrangement direction of the main discharge ports on at least one end side of the arrangement direction of main discharge ports at intervals larger than the intervals of the main discharge port arrangement for discharging liquid from the main discharge ports to a printing medium for printing, comprises the steps of discharging liquid from at least all the main discharge ports as a first step when liquid is discharged from the main discharge ports in order to make the discharge condition of liquid from the main discharge ports excellent; and discharging liquid at least all the sub-discharge ports as a second step. With the method thus arranged, when liquid is discharged from the main discharge ports to make the liquid discharge condition from the main discharge ports excellent, the step, in which at least all the sub-discharge ports discharge liquid, is provided besides the step in which at least all the main discharge ports discharge liquid. In this manner, the discharge amount of liquid from the main discharge ports are suppressed.
It is still another object of the invention to provide a cartridge which comprises a liquid discharge head provided with a plurality of main discharge ports arranged at predetermined intervals; at least one of sub-discharge ports on both end sides in the arrangement direction of the main discharge ports at intervals larger than the arrangement intervals of the main discharge ports in the arrangement direction thereof; a plurality of liquid chambers having these liquid chambers open;thereto; a common liquid chamber communicated with each of these liquid chambers, at the same time, liquid being supplied thereto; and a plurality of discharge energy generating units for generating discharge energy utilized for discharging liquid from the main discharge ports and the sub-discharge ports; and a liquid tank retaining liquid to be supplied to the liquid discharge head.
It is still another object of the invention to provide an image forming apparatus which comprises an installation unit for a liquid discharge head provided with a plurality of main discharge ports arranged at predetermined intervals; at least one of sub-discharge ports on both end sides in the arrangement direction of the main discharge ports at intervals larger than the arrangement intervals of the main discharge ports in the arrangement direction thereof; a plurality of liquid chambers having these liquid chambers open thereto; a common liquid chamber communicated with each of these liquid chambers, at the same time, liquid being supplied thereto; and a plurality of discharge energy generating units for generating discharge energy utilized for discharging liquid from the main discharge ports and the sub-discharge ports. With the apparatus thus arranged, liquid is discharged from the main discharge ports at the time of printing operation, but the discharge energy generating unit in the liquid chambers to which the sub-discharge ports are open do not generate discharge energy. Nevertheless, when the pre-discharging operation is executed prior to printing operation, liquid can be discharged from the sub-discharge ports, too. Also, since the sub-discharge ports are arranged at intervals larger than the arrangement interval of the main discharge ports, the resultant numbers of sub-discharge ports become relatively smaller than the conventional ones where all the discharge ports are arranged at specific intervals when liquid is sucked from the main discharge ports and sub-discharge ports, provided that the arrangement length of discharge ports is specific.
In accordance with the present invention described above, a plurality of main discharge ports are arranged at predetermined intervals in the arrangement direction thereof, and then, at least one of sub-discharge ports is arranged at intervals larger than the arrangement interval of the main discharge ports on both sides in the arrangement direction of the main discharge ports. Therefore, it becomes possible to perform pre-discharges by discharging liquid also from the sub-discharge ports when the recovery process is executed for a liquid discharge head. As a result, bubbles residing on both end portions of the common liquid chamber are exhausted together with liquid thus exhausted from the sub-discharge ports, hence making it possible to not only prevent drawback, such as color mixture, that may occur when different kinds of liquid enter the interior of liquid discharge head from the sub-discharge ports at the time of recovery process of the liquid discharge head performed by the overall suction operation, but also, suppress the amount of liquid to be sucked from the sub-discharge ports. Particularly, it becomes possible to promote the liquid flow between the sub-discharge ports, and the end portions of the long and narrow common liquid chamber to which liquid is supplied, and the overly viscous liquid residing on the end portions of the common liquid chamber in the longitudinal direction, which tend to be stagnated, can be exhausted outside the liquid discharge head from the sub-discharge ports smoothly and reliably.
When at least one dummy liquid chamber having no discharge port but communicated with the common liquid chamber is arranged between the liquid chamber to which the sub-discharge port is open, and the liquid chamber having the main discharge port open thereto, and being adjacent to this sub-discharge port, it becomes possible to function this dummy liquid chamber as a buffer.
Also, when the discharge energy generating unit is formed in the dummy liquid chamber, there is only a difference between the liquid chamber having discharge ports and the dummy liquid chamber in the aspect whether or not each of them has liquid discharge ports.
When the dummy liquid chambers and the liquid chambers having sub-discharge ports are arranged alternately, it becomes possible to suppress the amount of liquid to be sucked from the sub-discharge ports at the time of executing the recovery process for the liquid jet head.
When the opening area of the main discharge port is made larger than that of the sub-discharge port, it becomes possible to enhance the buffering function of the liquid chamber to which the sub-discharge port is open at the time of printing operation.
When the opening shape of the sub-discharge port is made different from that of the main discharge port, the buffer function is optimized of the liquid chamber to which this sub-discharge port is open.
When at least two lines of discharge ports are formed in parallel to each other at intervals of 600 dpi, respectively, with the displacement of half pitch from each other for the arrangement interval per line, it becomes possible to obtain a liquid discharge head capable of executing as high performance as 1,200 dpi. When the amount of liquid discharged from the main discharge port is set at 5 picoliters or less, it becomes possible to enhance the image resolution and improve the obtainable image quality significantly.
When the pre-discharging operation is executed prior to printing operation, it becomes possible to exhaust from the sub-discharge ports the liquid residing on the one end side in the longitudinal direction of the common liquid chamber, which is in the state of stagnation, by repeating the step where liquid is discharged simultaneously from one of sub-discharge ports and at least two of the main discharge ports adjacent to each other having the common liquid chamber between them.
When the step in which liquid is discharged simultaneously from one of sub-discharge ports and at least two of the main discharge ports adjacent to each other having the common liquid chamber between them, is repeated at the time of executing the pre-discharging operation is executed prior to the printing operation, the discharge operation from one of the sub-discharge ports is executed one after another from one end side in the arrangement direction of the main discharge ports, but liquid discharge operations for at least two of the main discharge ports adjacent to each other having the common liquid chamber between them are executed alternately from one end side and the other end side in the arrangement direction of the main discharge ports. In this case, vibrations are given to the liquid which is in the sate of stagnation on both end side of the common liquid chamber in the longitudinal direction. As a result, the flowability of liquid is promoted to make it possible to exhaust it from the sub-discharge ports reliable.
When liquid is discharged from the main discharge ports to make the liquid discharge condition excellent form the main discharge ports, it becomes possible to suppress the liquid which may be unnecessarily discharged from the main discharge ports.